Recovirus NS1-2 has viroporin activity that induces aberrant cellular calcium signaling to facilitate virus replication

Abstract

27Enteric viruses in the Caliciviridae family cause acute gastroenteritis in humans and animals, but 28 the cellular processes needed for virus replication and disease remain unknown. A common 29 strategy among enteric viruses, including rotaviruses and enteroviruses, is to encode a viral ion 30 channel (i.e., viroporin) that is targeted to the endoplasmic reticulum (ER) and disrupts host 31 calcium (Ca 2+ ) homeostasis. Previous reports have demonstrated genetic and functional 32 similarities between the nonstructural proteins of caliciviruses and enteroviruses, including the 33 calicivirus NS1-2 protein and the 2B viroporin of enteroviruses. However, it is unknown whether 34 caliciviruses alter Ca 2+ homeostasis for virus replication or whether the NS1-2 protein has 35 viroporin activity like its enterovirus counterpart. To address these questions, we used Tulane 36 virus (TV), a rhesus enteric calicivirus, to examine Ca 2+ signaling during infection and determine 37 whether NS1-2 has viroporin activity that disrupts Ca 2+ homeostasis. We found that TV disrupts 38 increases Ca 2+ signaling during infection and increased cytoplasmic Ca 2+ levels is important for 39 efficient replication. Further, TV NS1-2 localizes to the endoplasmic reticulum (ER), the 40 predominant intracellular Ca 2+ store and the NS2 region has characteristics of a viroporin domain 41 (VPD). NS1-2 had viroporin activity in a classic bacterial functional assay and caused aberrant 42 Ca 2+ signaling when expressed in mammalian cells, but truncation of the VPD abrogated these 43 functions. Together, our data provide new mechanistic insights into the function of the NS2 44 region of NS1-2 and show that like many other enteric viruses, enteric caliciviruses also exploit 45 host Ca 2+ signaling to facilitate their replication. 46 Importance 47Tulane virus is one of many enteric caliciviruses that cause acute gastroenteritis and diarrheal 48 disease. Globally, enteric caliciviruses affect both humans and animals and result in >65 billion 49 dollars per year in treatment and healthcare-associated costs, thus imposing an enormous 50 economic burden. Recent progress has resulted in several cultivation systems (B cell, enteroid 51 and zebrafish larvae) to study human noroviruses, but mechanistic insights into the viral factors 52 and host pathways important for enteric calicivirus replication and infection are largely still 53 lacking. Here we used Tulane virus, a calicivirus that is biologically similar to human 54 noroviruses and can be cultivated in conventional cell culture, to identify and functionally 55 validate NS1-2 as an enteric calicivirus viroporin. Viroporin-mediated calcium signaling may be 56 a broadly utilized pathway for enteric virus replication, and its existence within caliciviruses 57 provides a novel approach to developing antivirals and comprehensive therapeutics for enteric 58 calicivirus diarrheal disease outbreaks. 59 60 61The Caliciviridae family consists of small, non-enveloped single-stranded RNA viruses 62 with five ...

Leaked genomic and mitochondrial DNA contribute to the host response to noroviruses in a STING-dependent manner

“…We considered if the NS1-2 protein was the cause of leakage of DNA into the cytosol given that it has been suggested to be a viroporin [33]. The M2 protein of Influenza A virus and the 2B protein of EMCV have been shown to mediate leakage of mtDNA by upsetting the intracellular calcium balance in a manner dependent on their viroporin activity [12].…”

“…Next, we considered if any of the structural and non-structural viral proteins is the cause of leakage of DNA into the cytosol. One likely candidate is the NS1-2 protein that was recently shown to potentially have a viroporin activity [33]. We hypothesised that the NS1-2 protein, as a viroporin, may disrupt intracellular calcium homeostasis and eventually lead to mitochondrial leakage, similar to the M2 protein of Influenza A virus and the 2B protein of EMCV [12].…”

Breaking the Ice: A Review of Phages in Polar Ecosystems

“…Despite these differences, high spatial heterogeneity was found among dsDNA viral communities and pH was the most significant ecological driver of the dsDNA viral communities in the ice-free surface soils [174]. Notably, calcium content was also a significant ecological driver because calcium ions are related to several essential aspects of viral life, such as entry into host cells, genome replication, and building new viruses to invade other cells [175].…”